1. Field of the Invention
The present invention relates to an image forming apparatus that sets an output unit configured by a plurality of pages of which the order is determined as one copy and is capable of outputting a plurality of copies of output units, an image forming system that includes the image forming apparatus, and a computer-readable recording medium having a program.
2. Description of the Related Art
Conventionally, image forming apparatuses are known, each forms an image on a sheet based on image data and discharges the sheet on which the image is formed. The image forming apparatuses, for example, are a copying machine, a printer, a facsimile, a multifunction periphery, and the like. In the case where the image forming apparatus is a copying machine, the image forming apparatus acquires image data by reading an image from a document. On the other hand, in the case where the image forming apparatus is a printer, the image forming apparatus acquires image data from an external apparatus such as a personal computer.
As a method of using the image forming apparatus, there may be a case where the image forming apparatus outputs an output unit that is configured by a plurality of pages. In such a case, a checking operation is important to check whether or not a image is normally formed on a sheet. For example, in the checking operation, it is checked whether or not page missing, paging disorder, or the like occurs.
Here, in the case where a plurality of copies of output units are output, especially in production-based printing in which printing is performed on a massive scale, for manually checking page missing and paging disorder for an output material after output, a large quantity of processes is required. If an output material in which page missing or paging disorder occurs is delivered to a client, it results in a remarkable credit loss for the client.
Accordingly, it is preferable to automate the checking operation, and techniques for detecting page missing at the time of performing a printing operation are proposed in Patent Literature 1, 2 and the like.
In Patent Literature 1, an image forming apparatus is proposed in which identification information corresponding to each one of a plurality of pages is assigned to page data, and, by performing a calculation process that is based on the reading sequence of the page data, it is determined whether or not an image is normally formed on a plurality of sheets for output units other than the n-th copy by comparing a calculation processing result of the n-th copy and a calculation processing result of copies other than the n-th copy. More specifically, in the case where the calculation processing result of copies other than the n-th copy coincides with that of the n-th copy, it is determined that page missing, paging disorder, or the like has not occurred in the output units other than the n-th copy. On the other hand, in the case where the calculation processing results do not coincide with each other, it is determined that page missing, paging disorder, or the like has occurred, abnormality processing is performed, and the output process is stopped.
In Patent Literature 2, a technique (hereinafter, referred to as a first technique) is proposed in which a sum value of the numbers of pixels of a plurality of pages that configures the output n-th copy of unit and a sum value of the numbers of pixels of a plurality of pages that configure the (n+1)-th copy or after the (n+1)-th copy of output units are compared with each other. More specifically, in the case where sum values of the numbers of pixels coincide with each other, the image forming apparatus determines that page missing, paging disorder, or the like has not occurred in the (n+1)-th copy or after (n+1)-th copy of output unit. On the other hand, in the case where the sum values of the numbers of pixels do not coincide with each other, the image forming apparatus determines that page missing, paging disorder, or the like has occurred in the (n+1)-th copy or after the (n+1)-th of copy, performs abnormality processing, and stops the output process.